Case Study

Neck-Guided Air Conveyor 'Floats' PET Bottles to Eliminate Jamming

In the summer of 1996, engineers at the Pepsi-Cola plant in Piscataway, N.J. were having a serious jamming problem on their 2-liter PET line. Thirty to 40 jams were occurring in every 8-hour period, resulting in enormous downtime. To try and solve the problem, Pepsi substituted a lighter bottle for the 55-gram bottle. But the jams continued at an unacceptable level.

In August, a Crown Simplimatic Ring Jet air conveyor line was installed to replace the existing conveyor line, and the resulting change was dramatic. In the year following the installation, there were only 10 jams, a reduction of more than 99 percent.

How It Works
The Ring Jet system moves shaped or straight-walled plastic bottles by blowing air under their neck rings. (See Diagram A) This lifts the bottles slightly off the conveyor's neck guide and has the effect of floating the containers as they speed down a beverage production line from depalletizers to fillers. (See Photo A) Previously, other neck-guided air conveyors moved PET bottles by blowing air on the bottles' shoulders or into their top openings, or finish. These designs were not reliable because they allowed bottles to swing and tilt, damaging them and otherwise jamming filling lines.

Diagram A: Ring Jet air flow

Photo A

The Ring Jet conveyor can move 0.5-liter bottles at speeds of up to 1500 bpm (bottles per minute), and 2- and 3-liter bottles at speeds of up to 800 bpm. Even while moving at the high speeds, the bottles continue to be stable and well controlled. The conveyor system was developed for use in soft drink, bottled water, fruit juice and other beverage production plants as well as in plants where PET bottles are blow molded and conveyed onto pallets for delivery to filling plants.

No Need For Lubricants
Besides eliminating jamming problems, the Ring Jet design also eliminates two potential sources of contamination -- air blown into the bottles to move them, and lubrication needed on some neck rings. Stainless steel neck guides on some conveyors can create friction and require a lubricant to make smooth flow possible. Lubricants leave a residue on bottles and some attack the bottles' integrity. To avoid this problem, in Ring Jet installations the PET bottles move on low-friction, plastic strips, which are clipped to the neck guides, expediting smooth flow without the use of any external lubricants.

Easy Maintenance
The Piscataway plant's maintenance time savings have also been enormous, with the line requiring only about one hour of cleaning with a damp rag once a month compared to about 500 hours of annual maintenance needed with the prior system. Additionally, the new conveyor line did away with the need for "stick people", employees stationed throughout the line to clear jams with 15 foot poles.

Easy Changeover
The variety of new shapes and the light weight of plastic bottles (some weighing less than 28 grams) were among the principal factors that led to the development of the Ring Jet system. Designed with pneumatically controlled side guide rails for careful handling and quick changeovers, the conveyor can be easily customized to handle different sizes or shapes of PET bottles. (See Photo B) Changeover between bottle sizes, shapes and diameters is facilitated by a comparatively small number of adjustments.

Photo B

Easy changeover is particularly important in an installation in a blow molding plant where the line is running one-piece 2-liter soda bottles, 1- and 1 1/2-liter water bottles, and the 24-oz. Pepsi "Quick Slam" bottle. The Ring Jet conveyor is running "jam free," according to the customer, with no wild swings and less scuffing than other conveyors. The equipment was also described as contributing a 0.5 percent gain in productivity following a very quick startup with the equipment requiring only 3 days to meet standard.

Crown Simplimatic exhibited a working model of its new Ring Jet unit at Pakex 98, held March 30 - April 3 at the National Exhibition Centre in Birmingham, U.K.

Crown Simplimatic products and services include filling systems for carbonated and non-carbonated beverages; air and mechanical conveying systems, palletizing and depalletizing equipment (both bulk and case designs), container rinsing and bottle washing equipment, labelers, packing and unpacking machinery, and systems design and engineering services.

By Pam Ahlberg

For more information contact: Crown Simplimatic, P.O. Box 11709, Lynchburg, VA 24506. Tel: 804-582-1200; Fax: 804-582-1284.